Air lock and valve for pneumatic conveying systems



A. H. KORN AIR-LOCK AND VALVE FOR PNEUMATICI CONVEYING SYSTEMS Filed061.. 22, 1945 s sheets-smet 1 May 17, 1949. A, H, KORN 2,470,744

AIR-LOCK AND VALVE FOR PNEUMATIC CNVEYINGv SYSTEMS Filed OCT.. 22, 19453 Sheets-Sheet 2 To Fc-14. 7151.5. f1-qa.

T0 T0 INTERMEDIATE TO T0 INLET TG INTERMEDIATE. VALVE 5 VACUUM CHAMBERATMOSPHERE VALVE CHAMBER To aunar To vAcuuM i* vALvE 6 72 61 INVENroRArthunlZ/I'orn BY;

ATTORNEY May 17, 1949. A. H. KORN Y 2,470,744

AIR-LOCK AND VALVE FOR PNEUMATIC CONVEYING SYSTEMS Filed OM'. 22, 1945 3Sheets-Sheet 3 INVENTOR BY y l ATTORNEY Anika# Elforn UNITED STATESPATENT -orties AIR. LOCK AND VALVE FOR PNEUMATIC CONVEYING SYSTEMSArthur H. Korn, New York, N. Y., asslgnor to Airborne ConveyorsCorporation, New York, N. Y., a corporation of New York ApplicationOctober 22, 1945, Serial No. 623,750

7 Claims.

pressure applied at the transmitting end or by suction applied at thereceiving end. i Except at the inlet end of a vacuum system o l theoutlet end of a pressure system, the introduction and Withdrawal ofmaterial at any region Where the pressure condition within the system isdiilerent from that on the outside requires a valvular instrumentalityto permit the desired re' sult to be accomplished without impairment ofthe pneumatic condition within the system.

For example, at the receiving end of a vacuum system, the vessel orhopper Within which the material is collected (after segregation fromthe gas stream by centrifugal movement or the like) is under vacuum,iandthe withdrawal of the material is achieved by means of a so-calledairlock. This consists essentially of an inlet chamber in communicationwith the hopper, an outlet or discharge chamber, an intermediate chamber, valves between these chambers, and a means for making the pressurein the intermediate chamber alternately equal to the sub-atmosphericpressure in the hopper and the atmospheric (or other) pressure in theoutlet chamber. Whenever the intermediate chamber has a pressure equalto that in the hopper, the valve from the latter may be opened to allowthe collected material to pass into the intermediate chamber; andafterthis valve is closed, and after the pressure in the intermediatechamber has been equalized with that in the outlet chamber, the secondvalve may be opened to allow the material to be discharged. This cycleof operations is then repeated, and continues indefinitely.

In devices heretofore employed for this purpose, the valves have been ofmechanical character, either in the form of reciprocating or swinginggates or the like, or rotating elements,

and serious disadvantages and diilculties have arisen due to thetendency of the mechanical elements to become clogged, jammed, andunduly' abraded, requiring frequent costly repairs and replacements.Moreover, such devices are cumbersome, noisy, and expensive tomanufacture and to operate, and they present a serious problem inproperly maintaining the parts in properly lubricated conditionuncontaminated by the solid achieved by purely pneumatic means.

particles which are constantly passing through.

It is a general object of my invention to provide a simplified apparatusand mode of procedure whereby these and other disadvantages may besuccessfully overcome, and whereby solid material of the charactermentioned may@ be expeditiously moved into and out of a'pneumaticconveying system by means of a relatively simple andv inexpensive devicewhich is reliable and noiseless in operation and practically immune toabrasion and wear. The present improved apparatus is devoid of mechanismsuch as mechanical gates or the like, and those few moving parts whichare involved are either maintained at all times out of contact with thesolid-material, or are of such character as to be substantiallyunaffected by it in any deleterious manner.

The successful achievement of this desirable result is predicated uponthe special design and employment of a valve whose operation involvesnothing more than a slight deflection of a flexible element of rubber orequivalent material, and upon a special arrangement of two such valvesin a manner which permits their activation to be y In this way, I amenabled to utilize, for the operation of the device, the very pressuredifferentials Whose existence makes the use ofthe device necessary.

y This results in low cost of manufacture, simplicity and compact-ness,and high operating eiliciency. y

A particular feature of my invention resides in the ability to provideand employ a common continuously-operable control device for the meanswhich alternately varies the pressure in the intermediate chamber andfor the valve operations. This results in an automatic operation of theapparatus whereby it may be caused to function continuously withoutattention, the several procedures of the operating cycle being carriedout in repeated accurately-timed sequences.

Certain other features of my invention relate to the arrangement of theparts entering into the apparatus as a whole, while others are directedto details of the valves themselves.

'From a broad aspect, the invention relates to the movement-of materialfrom one region to another, where the regions are at diierent pressures.By way of example, I have herein chosen to illustrate my invention andexplain its use in the withdrawal of solid material from the receivingend of a suction-operated pneumatic system into a region of atmosphericpressure, but it will be understood that the broader phases of 3 myinvention are not necessarily limited in their applicability to any suchspeciiic purpose.

One way of achieving the foregoing general objectives and advantages,and such other objects and advantages as may hereinafter appear or bepointed out, is illustratively exemplied in the accompanying drawings,in which:

Figure 1 is a longitudinal cross-sectional view of an air-lock device ofthe present improved character;

Figures 2 and 3 are cross-sectional views taken substantially along thelines 2-2 and 3-3, respectively, of Figure 1;

Figure 4 is a longitudinal cross-sectional view through a control deviceof the preferred character;

Figures 5 and 6 are cross-sectional views along the lines 5-5 and 6-6,respectively, of Figure 4;

Figures 7 and 8 are obverse and reverse perspective views, respectively,of the relatively movable element of the control device;

Figures 9 and 10 are fragmentary, enlarged details of the valve seat,showing its mode of cooperation with the movable valve member; and

Figures 1l-16 are diagrammatic views, each similar to Figure 1, showingthe sequence of operations which are performed during one cycle.

Referring to Figures 1-3, it will be observed that the device consistsessentially of a conduit having a pair of valves arranged in tandemtherein, positioned at longitudinally-spaced regions. For the sake ofsimplicity of manufacture, and ease of assembly and disassembly of theparts, the conduit is preferably formed of three sections 20, 2| and 22,each of which is substantially tubular and is provided with flanges atits ends. Thus, the flange 23 on the section 20 facilitates itsattachment to the hopper (not shown) at the receiving end of asuction-operated pneumatic conveying system. This attachment may beeffected by means of bolts 24 or the like, as indicated in Figure 2.Similarly, the flanges 25 and 26 permit the sections 20 and 2| to bereadily assembled, by means of studs 21 or the like, as indicated inFigure 3; and the ilanges 28 and 29 cooperate in a similar manner tohold the sections 2| and 22 together.

For a purpose presently to be described, a ring 30 is introduced betweenthe anges 25 and 26,

and a similar ring 3| is introduced between the ilanges 28 and 29. Eachof these rings is split, l

i. e., it is made of two semi-circular parts.

In the section 20 I mount a tubular sleeve member 32, composed ofdeflectable material such as rubber or its equivalent. This member isconcentrically arranged with respect to the section 20, and has itsopposite ends sealed to the conduit so that a closed annular space 33 isprovided between the sleeve member 32 and the conduit Wall. In thiswall, there is a connection opening 34 by means of which the pressurewithin the annular space 33 may be varied, as will be presentlypointed'out. A similar tubular "sleeve member 35 is mounted inconcentric relation within the conduit section 22, its ends being sealedto the conduit wall so as to provide an annular space 36 between themember 35 and the conduit wall. Here, too, a connection opening 31 isprovided to permit the pressure in the annular space 36 to be varied.

The sleeve members 32 and 35 are substantially the same, being composedof the same general type of deiiectable material, and they differ onlyin the fact that the member 32 normally assumes the convex orbarrel-shaped contour shown in Figure 1 when the pressures on itsopposite sides s alongside of it. The ring 46 is of relativelyunvulcanized or otherwise iirmly secured to thev rings 38 and 39, andthe latter are mounted, respectively, in annular retaining memberssecured to the conduit wall, and provided with grooves to accommodatethe rings. The ring 38 is moun-ted\within a retaining member 40 whichilts in a suitable recess provided for this purpose in the end portionof the section 20. The retaining member for the ring 39 is thesplit`ange 30 hereinbefore mentioned. Each of the rings 38 and 39 clampsthe corresponding out-turned margin of the sleeve member 32 against theconduit wall, a sealed joint being thus produced. The member 40 may besplit, if desired, but this is not absolutely essential. In assemblingthe parts, the sleeve member 32 may be secured to the ring 40, thisassembly may then be inserted endwise into the section 20 until the ring40 seats itself as shown, and the two sections of the element 30 maythen be applied to hold the parts in the relationship illustrated,thenal step being merely the application and tightening of suitablestuds or fastening elements as indicated at 21 in Figure 3.

On the interior of the section 20, a series of ribs or projections 4|may be provided, for the purpose of lending support to the midportion cithe sleeve member 32 when it assumes the position shown in Figure 1. I

The sleeve member 35 is similarly mounted in association with thesection 22, its out-tumed ends being engaged around rings 42 and 43,respectively, the ring 42 being secured to an annular element 44, andthe ring 43 being supported within the split flange-like element 3|. Theelements 3| and 44 are provided with grooves to accommodate the rings.The section 22 may also be provided with interior ribs 45 or the like,to lend support to the midportion of the sleeve member 35 when thelatter is in its outwardly-deiiected position.

Each of the sleeve members 32 and 35 is adapted to deiiect between abarrel-shaped contour and a spool-shaped contour, this deflection beingachieved by variation of the pressures applied to the sleeve members.Whenever the sleeve members are deected inwardly, they establish contactwith corresponding centrally disposed valve seats; whenever they deectoutwardly, they bear against the ribs 4| and 45, respectively. 'I'heelliptical cross-sectional nature of the rings 38,l 33, 42 and 43permits tlese deflections to take place with a minimum of wear and tearand without any danger of undesirably weakening the sleeves at theiranchored ends.

The valve seat with which the sleeve 32 cooperates consists of a ring 46mounted on a tubular member 41, and a second ring 48 mounted yieldingmaterial, while the ring 48 is of relatively soft and yieldablematerial. 'I'he ring 43 has an, external diameter slightly greater thanthat of the ring 46. The purpose of this arrangement of parts will bedescribed more fully hereinafter in connection with Figures 9 and 10,

The supportingv tube 41 is cone-shaped, as shown, with the apex of thecone directed toward the incoming material.

A similarly-constructed valve seat is disposed centrally within thesection 22. and is adapted to be engaged by the sleeve member 35. Itconsists of a ring 49 'of relatively unyielding material and an adjacentring 59 of relatively soft yieldable material, the latter having anormal external diameter slightly greater than that or the ring 49. Theseats 49 and 59 are mounted on a tubular support I which is cone shaped,Aas shown.

The supports 41 and 5| may be held in proper concentric positions withinthe device by securing them both to a longitudinal rod or tube 52 whichis in turn supported Within the conduit by one or more spiders extendingradially into engagement with the central section 2| of the device. Onesuch spider is indicated most clearly in Figure 3, and has been shown asconsisting of three radial ns 53 whose outer ends are supported ingrooves 54 provided for this purpose on the interior surface of thesection 2|. A similar set of radial fins 55, similarly supported ingrooves 56, lends added supportvto the rod 52.

'I'hat region of the conduit which lies on the outside of the valve seat46--48 (i. e., the upper end of the conduit as viewed in Figure 1)constitutes what is hereinafter referred to as an inlet chamber. It isthis chamber which is constantly in communication with the hopper in thepneumatic conveying system. That portion of the` conduit which liesoutside of the valve seat 49-50 (i. e., the portion at the bottom asviewed in Figure 1) is hereinafter referred to as an outlet cham-ber,this chamber being in communication with the bin or other receptacleinto which the material is to be ultimately discharged. That centralportion of the conduit which lies between the valve seats constituteswhat is hereinafter referred to as an intermediate chamber. The pressurein this intermediate chamber can be varied by means of a connectionopening 51 formed in the wall of the central section 2l.

Before describing thefcontrol device by means of which the apparatus maybe automatically operated, reference is directed to Figures 11`16, whichdepict the successive procedures which constitute a single cycle ofoperation.

In Figure 11, both valves are closed, and a mass of solid material 58 isshown in the collection hopper 59 of the suction-operated pneumaticconveying system with which the present device is associated. The sleevemember 32 is retained in the closed position shown by virtue of the factthat atmospheric pressure has been introduced into the space 33. Theexistence of atmospheric pressure in this space is indicated in Figure11 by the letter A. This pressure being greater than the vacuum withinthe hopper 59, the sleeve member 32 is deflected into the spool-shapedposition in which it bears against its valve seat and keeps this upperor inlet valve closed.

The first step in the cycle of procedures is to adjust the pressure inthe intermediate cham ber so that it will be equalto the sub-atmosphericpressure in the hopper 59. This is achieved by connecting the opening 51with a source of vacuum as indicated by the arrow in Figure 11, and theresultant vacuum which is produced in the intermediate chamber is indi#-cated by the letter V.

In each of Figures 12-16, in a similar manner, the letter A indicatesthe existence of atmospheric pressure, and the letter V indicates theexistence of sub-atmospheric pressure or vacuum.

The second step is indicated in Figure 12. The pressures in theintermediate and inlet chambers having been equalized, a .vacuum.isproduced in the annular valve space 33, and since the pressures on theopposite sides of the sleeve member 32 are thus equalized. this valveassumes its normal open position, and the collected material 56 isthereby allowed to fall downwardly into the intermediate chamber. Asuitable screen may be mounted in the connection opening 51 to preventany of the material from passing into the pipe or conduit 51.

The next step consists in again closing the inlet valve. This isachieved by introducing atmospheric pressure into the annular space 33,as indicated in Figure 13.

The next step is indicated in lFigure 14, and consists in varying thepressure in the intermediate chamber so as to make itA equal to that inthe outlet chamber. This is achieved by disconnecting the pipe 51 fromthe source of vacuum, and establishing a connection, instead, to asource of atmospheric pressure.

As indicated in Figure 15, the next step consists in applying a vacuumto the annular space 36 surrounding the outlet valve. This causes thisvalve to open, and allows the accumulated material to pass from theintermediate chamber into and through the outlet chamber to the point ofultimate discharge or collection.

The final step is indicated in Figure 16 and consists in re-closing theoutlet valve. This is achieved by re-establishing atmospheric pressurein the annular space 36.

The cycle is then repeated, by varying the pressure in the intermediatechamber to make it again equal to the pressure in the inlet chamber, andthis restores the parts to the relationships and pneumatic conditionsindicated in'Figure 11.

It will be observed that the valves are of such character that astreamlined path of travel is afforded for the solid material whichpasses through the device. At no time does the solid material come incontact with any mechanical parts which might become damaged or abraded.

The smooth operation of the device requires.

of course, that the closing of each valve be firm and secure. It is forthe purpose of assuring this l result that each valve seat is composedof the two `portions hereinbefore mentioned. -In Figures 9 and 10, forexample, the rings 46 and 48 of the inlet valve have been shown on anenlarged scale, and the sleeve member 32 has been indicated in theprocess of closing.v In the event that one or more particles of thesolid material,

as indicated at 60, are positioned in the path of the member 32 as itapproaches the valve seat, these particles will necessarily contact therelatively yieldable ring 4,8 first. However, since this element is softand yieldable, the continued deflection of the sleeve member, asindicated in Figure 10, will compress the particles 60 into the element48, and this will assure a tight closure between the sleeve 32 and themain valve seat portion 46. Upon subsequent opening of the valve, thering 48 will spring back to its initial position, thus expelling thetemporarily-embedded particles 66 and allowing them to pass through thevalve opening.

The elements 46 and 48 may be composed of any suitable material. Forexample, the portion 48 may consist of softsponge rubber or itsequivalent readily compressible from the normal shape of Figure 9 intothe compressed condition indicated in Figure 10, and readily returnableby its inherent resilience to the normal position of Figure 9 whenpressure upon it is released. The portion 46 may also be composed ofrubber or its equivalent. but will be of relatively unyieldingcharacter.

The valve seat portions 49 and 50 are constructed and function in thesame way.

Reference is now directed to Figures 4-8, in which I have illustrated apreferred control device for automatically effecting the series ofoperations hereinbefore described in connection with Figures 11-16. Thecontrol device consists essentially of a relatively fixed member havingports communicating, respectively, with the inlet and outlet valves,with the 4intermediate chamber, and with the two different pressuresources. (Where the apparatus is used in connection with asuction-operated pneumatic conveying system for the purpose ofdischarging the collected material to a region at atmospheric pressure,the two pressure sources are (a) a source of vacuum and (b) theatmosphere itself.) It is preferable, of course, that the vacuum sourcebe the same as that which produces the suction in the conveying systemitself. Coupled with this relatively fixed member is a relativelymovable member which is provided with suitable passages for establishingcommunications, in predetermined sequences, between the two sources ofpressure, on the one hand, and the intermediate chamber and the valves,on the other hand. Y

In the preferred device illustrated, the relatively fixed member assumesthe form of a body having a substantially cylindrical bore therein, theports communicating with this bore. Such a member is designated by thereference numeral 6I, and the ports are designated by the referencenumerals 62-66. The port 62 communicates with the annular space 33surrounding the inlet valve member 32. The port 66, arranged dia..metrically opposite the port 62, is connected to the annular space 36surrounding the outlet valve member 35. The port 63 is of annular shape,and is connected to the source of vacuum. The port 64 is aligned withthe port 62 and is connected to the intermediate chamber, i. e., to theconnection pipe 51. The port 65 is also aligned with the port 62 and iscaused to communicate with the atmosphere.

The relatively movable member assumes the form of a substantiallycylindrical body 61 which ilts snugly within the bore in the body 6| andis adapted to be continuously rotated about its axis. As will bepresently pointed out, the member 61 is symmetrical about a longitudinalplane, the plane referred to being the plane of the paper as viewed inFigure 4, and for this reason the member 61 may be rotated in eitherdirection with the same effect. For the purpose of explaining theoperation, it will be assumed that this member is rotated continuouslyin the direction of the arrows 68 of Figures 4 6.

Adjacent to one end of the member 61 and in alignment with the ports 62and 66, a passage 69 is provided which extends arcuately throughslightly more than 180 and communicates at its end with the atmosphere.Its controlling edges are designated by the reference numerals and 1i inFigures 1 and 8.

On the same side of the member 61, but nearer its opposite end, there isan arcuate passage 12 which is co-extensive in its longitudinaldimension with both ports 64 and 65. Whenever it communicates with theseports. it establishes a connection between the intermediate chamber andthe atmosphere. Its operative edges are designated by the referencenumerals 13 and 14 in Figure 8.

On the side of the member 61 shown in Figure 7, and corresponding tothat portion which is uppermost in Figures 4-6, there is an arcuatepassage 15 which is co-extensive in its longitudinal dimension with theports 62, 63 and 64. In its arcuate dimension it has a relatively narrowportion which aligns with the ports 62 and 66, the operative edges ofthis portion being designated by the reference numerals 16 and 11 inFigure '1; and it has a relatively wider portion whose operative edgesare designated by the reference numerals 16 and 19.

The disposition of, the parts, as shown in Figures 4-6, corresponds tothe state of affairs depicted in Figure 12. Thus, through the passage 15a communication is established between the source of vacuum 63 and boththe inlet valve and the intermediate chamber; through the passage 69 acommunication is established between the output valve and theatmosphere. The passage 12 is momentarily inoperative.

As the edge 10 sweeps across the port 62, com munication is establishedbetween this port and the'passage 69. This connects the inlet valve tothe` atmosphere and brings about the state of aiairs indicated in Figure13. This atmospheric connection is maintained until the edge 1l reachesthe port 62, and thus leaves the port 62 in communication with theatmosphere throughout the steps indicated, successively, in Figures 13,14, l5, 16 and 11.

Shortly thereafter, the edge 13 sweeps across the port 64, andestablishes communication between this port and the passage 12, therebyconnecting the intermediate chamber to the atmos phere and bringingabout the state of affairs indicated in Figure 14. This connection tothe atmosphere continues until the edge 14 sweeps across the port 64,and the connection between the intermediate chamber and the atmosphereis thus maintained throughout the steps indicated in Figures 14, 15 and16.

As the edge 1l presently sweeps across the port 66, it discontinues theconnection between the outlet valve and the atmosphere, and as the edge11 sweeps across the port 66 it establishes connection between theoutlet valve and the passage 15, hence with the source of vacuum, andthis brings about the state of affairs indicated in Figure 15.

Shortly thereafter, the edge 16 sweeps across the port 66,and'disconnects the vacuum communication. Then, as the edge 10 sweepsacross the port 66, connection between the outlet valve and theatmosphere, through the passage 69, is again established. This bringsabout the state of affairs indicated in Figure 16, and this state ofaffairs is maintained throughout the stages indicated, successively, inFigures 16, ll, 12, 13 and 14.

The next edge to become operative is the edge 19 which sweeps across theports 63 and 64 and establishes a communication, through the passage 15,between the intermediate chamber and the source of vacuum, thus bringingabout the state of affairs indicated in Figure l1.

Very shortly thereafter, the edge 11 sweeps across the port 62, andthereby brings the inlet valve also into communication with the vacuum,through the passage 15, thereby re-establishing the conditions indicatedin Figure 12, the parts being now restored to the relationship shown inFigures 4-6.

'I'he body 8l may be continuously rotated by l any convenient relativelyinexpensive source of power, such as an electric motor or the like. Itis preferably tapered to a slight extent, as indicated upon anexaggerated scale in Figures 4 8, to compensate for wear. It may befreely lubricated so that it will rotate smoothly and emciently, andthereis no danger of contamination since none of the parts of thecontrol device ever comes in contact with the material passing throughthe device.

It will thus be observed that I have provided an apparatus of unusualsimplicity, yet highly eiilcient and reliable in carrying out thedesired purpose of continuously withdrawing material from the pneumaticconveying system. In operation, the apparatus functions smoothly andnoiselessly, and can safely be relied upon to operate over long periodsof time without interruption and without requiring any special care.

It will be understood that changes in many of the details hereindescribed and illustrated may obviously be made by those skilled in theart without necessarily departing from the spirit and scope of theinvention as expressed in the appended claims.

Having thus described my invention and illustrated its use, what I claimas new and desire to secure by Letters Patent is:

1. In a pneumatic system including regions of different pressure, anair-lock interposed between said regions and comprising inlet and outletchambers and an intermediate chamber, the inlet and outlet chamberscommunicating respectively with said regions of different pressure,means for varying the pressure in said intermediate chamber to make italternately equal to said different pressures, a pair of valvespositioned between the intermediate chamber and the inlet and outletchambers respectively, each valve comprising a centrally disposed valveseat and a deiiectable tubular sleeve surrounding said valve seat andadapted to deflect into and out of a valve-closing position in contactwith said valve seat, the deilections of said sleeve being responsive tothe pressures on its opposite sides. and means for subjecting theopposite sides of each sleeve to said diiierent pressures in apredetermined timed sequence to establish communication between thechambers whose pressures have been equalized and to seal oftcommunication between the chambers whose pressures are different.

2. In a pneumatic system, the combination of elements set forth in claim1, one of said deiiectable sleeves having a normal shape in which it isin contact with the valve seat to close the valve, the other having anormal shapein which it is out oi contact with the valve seat to openthe valve, the valve which is normally closed being positioned adjacentto the region oi. greater pressure.

3. In a pneumatic system, an air-lock coniprising a conduit whoseopposite ends communicate with regions of difierent pressures, a valvein each of two longitudinally-spaced sections of the conduit andcomprising a valve seat centrally disposed in said section and a tubulardeilectable sleeve member surrounding said valve seat, means sealing theends of each sleeve member to the conduit, each sleeve member beingadapted to deilect into and out of contact with its valve seat inresponse to differences in pressure on its opposite sides, and means forestablishing communications at predetermined times and in predeterminedsequence between the annular spaces surrounding said sleeve members andsaid regions of diierent pressure. 4

4. In a pneumatic system, the combination set forth in claim 3, eachsleeve member having each of its end margins turned outwardly, and saidsealing means comprising a ring disposed beneath each out-turned marginand clamping the latter against the conduit wall.

5. In a pneumatic system, the combination set forth in claim 3,eachsleeve member having each of its end margins turned outwardly, andsaid sealing means comprising a ring disposed beneath each out-turnedmargin and clamping the latter against the conduit wall, said ring beingelliptical in cross-section with the major axis parallel to the conduitaxis, the conduit Wall being provided with annular grooves toaccommodate said rings.

6. In a pneumatic system, the combination with the elements set forth inclaim 3, of an axial post connecting said valve seats, and a supportingspider carried by said post and secured to 'the conduit wall in theregion between said sleeve members.

7. In a pneumatic system, the combination set forth in claim 3, eachvalve seat comprising a relatively unyielding portion and an adjacentportion of readily-compressible material having an external diametergreater than that of said unyielding portion.

ARTHUR H. KORN.

REFERENCES CITED The following references -are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,709,949 Rasmussen et a1. Apr.23, 1929 1,861,726 Trout June 7, 1932 1,873,138 Mitchell Aug. 23, 19321,943,589 Domina Jan. 16, 1934 1,970,021 Peters et al Aug. 14, 19342,060,748 Roberts et al. Nov. 10, 1936 2,071,197 Burns et al. Feb. 16,1937 FOREIGN PATENTS Number Country Date 360,943 Great Britain Nov. 9,1931

